Polygonal fuel cell

ABSTRACT

A polygonal electrochemical fuel cell comprises an outer film screen, independent channels conducting air and water, a reactant gas chamber defined by a corrugated multi-prong and multi-layered wall. The outer film screen attached to the rounded chamber wall prongs, which are equidistantly and circumferentially positioned on said chamber wall, defines polygons of the cell.  
     The curvilinear chamber wall provides a compact, structurally strong, lightweight and inexpensive cell design increasing the current working surface area and respective current output by 40% in comparison with the analogous tubular cell design. The cell polygons allow a substantially gap-free attachment of the adjacent cells to form modules of various shapes and without bulky edge and bipolar plates, gaskets, screws and other connectors present in traditional cells. The multi-functional gas chamber wall serves as a cell frame, water drain conduit, pressurized gas container and electric current connector.

BACKGROUND OF THE INVENTION

[0001] This invention relates to electrochemical fuel cells and moreparticularly to their most efficient and compact structural designs forgenerating electric current. The prior art is replete with hydrogen fuelassemblies for passing a hydrogen-containing gas through the electrolytemember and reacting with the oxygen atoms to form water and generate anelectrical current in the anode and cathode system. For example, U.S.Pat. No. 5,509,942 by Dodge disclosed a hydrogen fuel cell utilizingwith a plurality of layers of planar members, such as a layered porousanodic electrode, a solid electrolyte and a layered porous cathodicelectrode exposable to oxygen, to form tubular and frusto-conical cellswith concentrical layers. Connectors, screws, plates and links join thetubular cells to form a cell battery.

[0002] U.S. Pat. No. 6,063,517 by Montemayor teaches a spiral wrappedcylindrical proton exchange membrane cell including a planar anodeionically communicating with a catalyst and a sleeve defining a hydrogenflow path. U.S. Pat. No. 6,007,932 by Steyn discloses a tubular fuelcell with a porous tubular substrate and a plurality of flexible polymerelectrolyte fuel cells wound in side-by-side relation onto thesubstrate. U.S. Pat. No. 5,458,989 by Dodge discloses a tubular fuelcell and utilizing hydrogen-containing connectors, frames and batteriesor banks of parallel mounted fuel cells. U.S. Pat. No. 6,001,500 by Bassdiscloses a cylindrical fuel cell and a method of its manufacturing.

[0003] A typical fuel cell provides for supply of the reactants, such ashydrogen and oxygen, transportation of water and inert gases (nitrogenand carbon dioxide from air), and electrodes to support a catalyst,collect electrical charge, and dissipate heat. Such a cell usually hascathodic and anodic electrodes and an electrolyte sandwiched betweenthem. Fuel cells use ion transfer thorough the membrane- to produceelectrochemical reactions between the reactants (hydrogen gas at theanode and oxygen from ambient air at the cathode), which are suppliedfrom each electrode side of the membrane from an external tank or othersource. An ambient air forced to flow through the fiber cathodeelectrode and react with the catalyst layer of the cathode electrode tocause a chemical reaction for production of current and water. Besideselectrical and thermal resistance, reactant pressures and temperatures,the surface area and geometry of the cell structure are the main factorsaffecting the performance, occupied space and efficiency.

[0004] None of the prior art references known to the inventor disclosesthe present invention shown and described herein.

SUMMARY OF THE INVENTION

[0005] A novel polygonal electrochemical fuel cell comprising aplurality of independent gas channels circumferentially located aboutthe reactant gas chamber. The corrugated multi-layered chamber wall withthe rounded equidistant prongs and an outer film screen wrapped aroundthe circumferentially positioned prongs form the gas channels. Thescreen shell attached to the prongs defines the cell polygons. Thecorrugated wall structure and polygonal shape of the cell provide for arigid, compact, light and inexpensive structure, and the increasedelectric current production surface with the respective direct currentoutput. The polygonal cells may be joined together along their polygonsin a substantially gap-free arrangement without screws, links or otherstructural support in various modular combinations.

[0006] The unique compact design reduces a cross-sectional area orfootprint of the cell and increases its output, while allowing agap-free and connector free union of the cells in any space-fittingpattern.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a schematic longitudinal cross-sectional view of a fuelcell.

[0008]FIG. 2 is a schematic lateral cross-sectional view of the fuelcell showing the chamber prongs and gas channels.

[0009]FIG. 3 is a partial lateral cross-sectional view of the fuel cellshowing the channel wall details.

[0010]FIG. 4 is a schematic lateral cross-sectional view of oneembodiment of a fuel cell bank.

[0011]FIG. 5 is a schematic lateral cross-sectional view of anotherembodiment of the fuel cell assembly.

DESCRIPTION OF THE INVENTION

[0012] As shown in FIG. 1, a polygonal fuel cell 10 comprises an outerscreen shell 12 wrapped around a multi-layered corrugated gas chamberwall 14, which separates the gas chamber 16 from the longitudinalchannels 18. The wall channels 18 contain one type of reactant gas, suchas oxygen or air, and the chamber contains another type of reactant gas,such as hydrogen. Active reactant gas enters the chamber 16 through theinlet opening 20 in the chamber bottom plate 22 and exits through theoutlet opening 24 in the chamber top plate 26. The outer shell 12 may bemade from a thin, dielectric, air permeable, and waterproof film screen.The foldable outer screen extension 28 protrudes beyond the top andbottom plate levels in order to eliminate possible shortcuts between theadjacent cells in a stack.

[0013] The corrugated chamber wall 14 comprises a number ofequidistantly spaced rounded prongs 30. The convex wall segments 32merge with the wall concave segments 34. The corrugated wall edges areglued together at the longitudinal side seam 36 as shown in FIG. 3. Thescreen shell 12 covering the wall convex parts 32 defines the cell'spolygon shape, such as an octagon, hexagon and so forth. Each polygon orside 38 spans the space between the nearest prong convex tips. Thechannel or chamber wall 14 constitutes a multi-angled secant withrounded angle ends or prongs 30. The rounded prongs 30 are equidistantlylocated about the chamber's periphery.

[0014] The polygonal shape of the shell creates a smaller “footprint”than the than the respective tubular shape 40 by the area of truncatedsections 42. This area reduction minimizes the cell containing space,which is one of the advantages of the subject invention. Anotheradvantage is that the working surface of the curvilinear chamber wall12, combining its convex parts 32 and concave parts 34, greatly exceedsa cylindrical or tubular shape of the existing fuel cells.

[0015] The outer shell is glued or otherwise rigidly affixed to theseprongs. The chamber wall 14 serves a dual function of a structural frameof the cell and current producing element. As shown in FIG. 3, the wall14 comprises an inside current collector mesh 44 separated from theouter current collector screen 46 by an active element or electrode 48.The wall edge connection by the seal 36 contributes to the lightweightstructure of the novel fuel cells.

[0016] As shown in FIG. 4, fuel cells may be combined in rows in orderto fit a planar battery 50. Air or equivalent reactant gas may be causedto flow through natural convection as exemplified in the standalonelinear cell bank shown in FIG. 4. In this embodiment, the cells 10 couldbe secured to each other within the canister (bank) or be free standing.In this case, the air flows normally to the lateral area of activeelement of the chamber wall.

[0017] The air may be supplied via forced convection to the cellassembly as shown in another embodiment of the cell package (cellscontacting one another by the faces of the polygon) in FIG. 5. The airis propelled through the channels along the cell's longitudinal axis.The fuel cells may be glued or otherwise united to each other innumerous fitting patterns of tightly abutting cell polygons 52, withoutscrews or other kind of connectors, to build cell modules 54 as shown inFIG. 5. The substantially connector-free and gap-free cell connectionprovides the cell space saving and facilitates cell package patterns,which could fit any angular, multi-prong, corner or circular space. Thefuel cells may also be joined or stacked along their longitudinal axisfor a desired length of the cell line.

[0018] An output of electric current generated by a chemical reactionbetween the gases and the channel wall material exceeds the knowntubular fuel cell outputs due to the increased current-producingsurface. This translates into a gain in the lateral area-to-volumeratio, which is the ratio of the length of the secant to the area of thecross section. The subject design increases the secant-to-area ratio bymore than 40% in comparison to an equivalent circle.

[0019] Water generated during the fuel cell work and accumulated in thechannels is drained either by gravitation (e.g. in breathing bankembodiment shown in FIG. 4) or pressurized airflow (applicable to thecell assembly embodiment illustrated in FIG. 5) without danger ofshortcuts between the adjacent cells. A star (“snowflake”)cross-sectional design enhances the fuel cell gravimetric and volumetricpower through the increased surface-to-volume ratio and the cell'ssimplified geometric design. A plurality of independent channelscircumferentially located within the cell “occupy” the chamber spacewithout any negative effect on the gas supply through the chamber.

[0020] The subject cell design eliminates drawbacks of cylindrical andflat plate assemblies, which utilize bulky bipolar plates, frames,massive screws and other connectors. The curvilinear shape of the walladds to the wall's structural strength and rigidity in comparison to thestraight beam-like plate. The novel cell is significantly lighter andcheaper than comparable existing devices due to elimination of graphiteplates, cooling plates, end plates, massive rods, Teflon gaskets andother elements of traditional fuel cell supporting structures. Thechamber wall provides a frame and structural support for the cell andfor the module of cells being joined together for combined currentoutput.

[0021] The cell construction lends itself to unlimited modular cellcombinations of various shapes and sizes. The cell frame structureallows the substantially gap-free and connector-free cell stacking inlateral and longitudinal directions. Cooling, mass transfer managementand maintenance functions become easier and simpler than the same intraditional devices.

[0022] Although the present invention has been described with referenceto a preferred embodiment, it will be understood by those skilled in theart that numerous changes, omissions and additions may be made withoutdeparting from the spirit and scope of the subject invention.

We claim:
 1. A polygonal electrochemical fuel cell comprising: An outershell encompassing a corrugated chamber wall of the gas-passing chamber;Said shell and said chamber wall defining a plurality of independent gaschannels; Said channels located outside and about said chamber wall;Said chamber wall comprising layers of current collector and electrodeelements.
 2. The polygonal electrochemical fuel cell of claim 1, andfurther comprising: Said chamber wall comprising a plurality of prongs;Said outer shell being wrapped around said prongs; A plurality of cellpolygons being formed by the shell sections spanning said prongs.
 3. Thepolygonal electrochemical fuel cell of claim 1, and further comprising:Said chamber including an inlet and outlet openings for the reactant gaspassing through the top and bottom ends of said chamber; and Said outershell being made of air permeable and waterproof material.
 4. Thepolygonal electrochemical fuel cell of claim 1, and further comprising:Said chamber wall edges being sealed together to form a longitudinalside seam along the cell.
 5. The polygonal electrochemical fuel cell ofclaim 1, and further comprising: Said chamber wall providing astructural support for said cell and producing electric current as aresult of chemical reaction of reactant gases passing through said wall.6. The polygonal electrochemical fuel cell of claim 1, and furthercomprising: Said independent channels circumferentially located aroundsaid gas chamber; Said chamber wall layers including an inner currentcollector mesh, outer current collector mesh and an electrode means. 7.The polygonal electrochemical fuel cell of claim 1, and furthercomprising: Said chamber wall prongs being rigidly secured to the outershell; Said prongs equidistantly positioned about said chamber.
 8. Thepolygonal electrochemical fuel cell of claim 1, and further comprising:Said chamber including an inlet and outlet openings for the reactant gaspassing through the top and bottom ends of said chamber; Said outershell being made of air permeable and waterproof material; Said wallforming a frame structure providing lateral and longitudinal rigidityfor said cell.
 9. The polygonal electrochemical fuel cell of claim 1,and further comprising: Said channels being a conduit for draining thefluid produced as a result of electrochemical reaction between the gasespassing through the chamber, chamber wall and said channels.
 10. Apolygonal electrochemical fuel cell comprising: A reactant gas chambercomprising a corrugated multi-layered wall with a plurality of roundedprongs being enclosed by an outer screen; Said prongs located about saidwall; Said wall and outer screen forming a series of longitudinalreactant gas channels; Each of said channels being a conduit fordraining water being produced as a result of a chemical reaction betweenthe reactant gases flowing through the chamber, chamber wall and thechamber surrounding channels.
 11. The polygonal electrochemical fuelcell of claim 10, and further comprising: Said screen forming polygonsbordered by said rounded prongs; and Said screen being made from an airpermeable and water-resistant material.
 12. The polygonalelectrochemical fuel cell of claim 10, and further comprising: Saidouter screen having a foldable extension protruding beyond the chamberwall.
 13. The polygonal electrochemical fuel cell of claim 10, andfurther comprising: Said chamber wall providing structural strength forthe longitudinal and lateral stacking of the cells in a substantiallygap-free and connector-free manner; Said chamber wall being a part ofair and water transportation conduit outside the gas chamber; Said wallcomprising a catalyst and current collector meshes; Said gas chambershaving an inlet and outlet openings in its top and bottom elements forpassing the pressurized gas through the chamber; and An outer shellextension protruding beyond said wall.
 14. A polygonal electrochemicalfuel cell assembly comprising: A plurality of polygonal fuel cellsabutting the polygons of one another in a substantially gap-free andconnector-free manner; Each of said cells comprising a corrugatedmulti-layered gas chamber wall; Said wall providing a rigid framestructure for said cell; Said wall being surrounded by a plurality ofreactant gas channels within each cell; and Said cells providingstructural self-support for said assembly.